The 1908 Tunguska event was most likely an asteroid.
There is current information pointing to the facts of
asteroids colliding with earth on a very frequent basis.
Recent programming on informational TV programming has
shown where astronomers have been trying to keep track of the number
of asteroids in our (Earth) proximity. They have tried
to enlist the help of the military satellites to no avail.
It is suspected that two major collisions occur every two weeks.

-- Lowell
5/6/98 (#3)

Tunguska Event

We must keep in mind the idea that the explosion that occured in Tunguska in 1908 could very well have been
a "black hole". It has been theorized that black holes are
interdimensional gateways. A literal
rip in space and time occurs in a black hole. I belive that if you go to the North pole and then take an energy as great as that of the South pole and put them right next to eachother you could create a pull strong enough to open a temporary black hole.

There is evidence alluding to the fact that the explosion at Tunguska, Russia was an
experimental wireless transfer of highly focused electricity originating from Manhatten Island. Nikola Tesla conducted experiments with electricity, even one he dubbed his "death ray". He aimed for the North Pole but it is plausible that he overshot and hit Russia.